1. Field of the Invention
This invention pertains to circuit breakers of the type comprising a latched stored-energy mechanism releasable to effect tripping and, more particularly, it pertains to trip means automatically operable in response to overload conditions to effect release of the releasable mechanism.
2. Description of the Prior Art
In recent years, some circuit breakers with electronic trip units have employed replaceable rating plugs which comprise a resistor and an interlock means. The resistor is used to calibrate the electronic trip circuit. Rating plugs containing resistors of different values enables a rating change of the circuit breaker in the field. Interlock means are used to automatically trip the circuit breaker if the circuit breaker is closed when the rating plug is removed and to maintain the circuit breaker in a tripped condition as long as the rating plug is removed.
Interlock means employed in the past have consisted of a threaded device which when turned a number of full 360.degree. rotations pulls against a spring and moves a lever away from a trip latch so that the circuit breaker can be reset and closed. Such an interlock requires a careful and precise adjustment at the time of manufacture to ensure proper operation. Moreover, the user is required to turn the rating plug screw several full turns before the breaker can be reset and closed. One prior art circuit breaker is disclosed in the patent to Alfred E. Maier and Alan B. Shimp, U.S. Pat. No. 3,826,951.